This invention relates to a blood reservoir in a closed oxygenator circuit for temporarily collecting venous blood drained from a patient, and more particularly, to a small-sized venous blood reservoir intended for use in an oxygenator circuit for a neonate or infant.
Conventional venous blood reservoirs of closed type are designed (1) to have a sufficient volume to contain a predetermined volume of blood in order to provide a blood collecting function, (2) to control the blood collecting space or blood flow so as to remove air mixed in the drained blood, and (3) to prevent local blood stagnation within the reservoir.
To achieve air removal from the drained blood, the blood reservoir should have a space of dimensions sufficient for collecting blood therein. Differently stated, a room for blood stagnation should intentionally be provided. This is contrary to the above-mentioned requirement (3). More difficulty arises in manufacturing a flood reservoir of a smaller volume.
In order to overcome these difficulties, attempts have been made to remove air from the drained blood by controlling the blood flow in the blood collecting space. One such technique is to form a plurality of blood inlet openings around the top end of the blood inlet tubing through which blood enters the reservoir as a diffused gentle stream, thereby allowing air bubbles to come up by F buoyancy as disclosed in U.S. Ser. No. 439,422 (European Pat. No. 80610). Another technique is to provide an area for blood stagnation between the blood inlet and outlet of the reservoir.
A venous blood reservoir for an oxygenator cirucit of the type to be used for a neonate or infant requires an undesirably increased volume of priming blood unless it is made smaller in size than that for an adult.
Such a small-sized venous reservoir is very difficult to successfully remove air from the drained blood and to achieve debubbling by the conventional debubbling process employed in adult blood reservoirs.
In addition, when the blood reservoir of this type is bulged with blood, the reservoir made of a flexible vinyl chloride resin tends to give way at the intermediate thereof. Air bubbles collect and cling to the inside wall of the waisted portion and such clinging bubbles are difficult to remove therefrom. There is the need for an improved reservoir capable of preventing formation of such a waisted portion.